The present invention relates to air filtering units, and more particularly to air filtering units to be mounted in an air carrying conduit for filtering air as it passes between the conduit and a room.
In recent years, there has been considerable effort to provide rooms with a clean controlled environment. One criteria for a clean environment is a minimum amount of impurities, such as airborne dust, dirt and the like.
One of the major problems faced in accomplishing the filtration of airborne impurities from the air flowing between a room and an air carrying conduit has been the elimination of leakage around the juncture of a filter unit and the conduit. This problem been solved by heretofore known filter devices, however, the solution involved a complicated array of filter unit mounting components which have added substantially to the cost of manufacturing, shipping, installing and maintaining the filter units. A further drawback of these heretofore known units is that the seal preventing leakage between the juncture of the filter unit mounting components and conduit is broken when removing the filter. Another drawback, in some applications, has been the absence of means for controlling the amount of air flow from the conduit through the filter.
Therefore, a need exists for a filter unit having a minimum number of components, which effectively seals against leakage at the juncture of the filter unit and air carrying conduit and which allows the filter unit conduit seal to remain undisturbed when removing the filter. Further, there exists, in some applications, an additional need for means for regulating the amount of air flowing from the conduit through the filter.